The popularity of built-in kitchen counters and cabinets has created a common problem of how to provide accessibility to the corner space underneath the counter and/or in the wall cabinets which frequently are built on adjacent walls and meet in a corner. Typical prior art approaches to the problem of the corner cabinet involve the use of a circular shelf built on a pivot of one kind or another, often with a forty-five degree angle door or even a ninety-degree angle door placed on the inside corner of the cabinet face, the latter involving the cutting of a ninety-degree corner out of the shelf. Patents showing such structures are U.S. Pat. Nos. 2,239,734, 2,629,643, 2,693,401, 3,160,453, and 4,146,280. A lazy susan configuration which permits adjustment of the position of the rotating mechanism tends to have a particularly large number of parts--see U.S. Pat. No. 4,433,885.
Referring now to an art quite removed from the cabinet art, it is known to drill square holes utilizing a drill bit based on the geometry of curves of constant width, particularly the triangular curve of constant width sometimes referred to as the Reuleaux triangle. U.S. Pat. No. 4,074,778 describes such a drill bit and a gear mechanism to power it, in which cutting blades may be positioned at the apexes of a triangular curve of constant width. See also U.S. Pat. Nos. 4,012,077 and 4,062,595 which employ a related mechanism for coal mining. The reader may also be interested in early U.S. Pat. Nos. 1,241,175, 1,241,176, and 1,241,177, the article in Scientific American of February 1963, page 148, which is cited in the aforementioned U.S. Pat. No. 4,074,778, and the original and classic review of the properties of the curved triangle of constant width by Franz Reuleaux, entitled "The Kinematics of Machinery", Dover Publications Inc., New York 1963 pp 131 to 168, which was originally published in 1875. A typical illustration of a curve of constant width shows a triangular curve of constant width rotating within the confines of a square, always in contact with one point on each side of the square. See also Krayer and Hronas U.S. Pat. No. 3,369,320, which employs an "expansion" of the Reuleaux triangle.
Prior to the present invention, no one has applied the geometry of the Reuleaux triangle or any other closed curve of constant width other than a circle to the problem of the common corner cabinet, to my knowledge.